If you really want to run a Registry cleaner. The only one I recommend allowing the registry to be cleaned is through
What's new - Windows Live OneCare safety scanner for Windows Vista and Windows 7
But I do not know if the registry cleaner is part of this for 7. I do know that it is part of the XP side of the cleaner. But you can not run that one on 7.
So, you can try that, and if the reg cleaner is in there, it will do it for you and is the only recommended one to use.
However, if you do know what you are doing.
But, you are on your own if you mess up your system trying to mess with the Registry.
is
CCleaner.
Again, You are on your own and have been warned about messing with the registry and registry cleaners.
Also, as for defrag. Windows 7's built in defrag is all you need.
If you try running a different defrag and do not (which most people don't) turn off the background defrag in windows, your system will be working overtime trying to keep the system defragged the way Windows wants it. There really isn't much use for a third party defrag unless you use it to defrag individual large files.